The production of a highly integrated semiconductor element generally has a series of processes as follows: a conductive thin film such as a metal film as a conductive wiring material and an interlayer dielectric film for insulation between conductive thin films are formed on an element such as a silicon wafer; after that, a photoresist is uniformly applied to the surface thereof to provide a photosensitive layer, and this is subjected to the selective exposure/development treatment to form a desired resist pattern; then the dry etching treatment is applied to the interlayer dielectric film using the resist pattern as a mask to form a desired pattern on the thin film; and then the photoresist is completely removed by ashing with oxygen plasma or cleaning with a cleaning solution.
Recently, the miniaturization of design rules has been accelerated, and the limit of high-speed arithmetic processing has been gradually controlled by signal transmission delay. For this reason, the conductive wiring material has been changed from aluminium to copper which has lower electrical resistance, and the interlayer dielectric film has been changed from a silicone oxide film to a low dielectric constant film (a film having a dielectric constant of less than 3, hereinafter referred to as “low-k film”). With the miniaturization of wiring, a material containing tungsten having high heat resistance is used for a contact plug for connection to a substrate. In addition, with the miniaturization of design rules, the constitution of the gate of the transistor has been gradually changed from a combination of silicon oxide and polycrystalline silicon to a combination of a high dielectric constant material and a metal. There is a case where a tungsten-containing material is used as this metal. Further, in aluminium wirings, a tungsten-containing material is used for a contact plug which connects wirings of different layers.
In the process for manufacturing a semiconductor element using a tungsten-containing material, when a photoresist is removed with oxygen plasma, there is a problem that a low-k film is damaged due to exposure to oxygen plasma or the like, resulting in significant deterioration of electrical characteristics. In addition, the tungsten-containing material is damaged due to exposure to oxygen plasma or the like, resulting in problems in production processes after that. For this reason, in the production of a semiconductor element using a low-k film and a tungsten-containing material, it is desired to suppress damage to the low-k film and the tungsten-containing material while removing a photoresist at a level comparable to that of an oxygen plasma process.
Regarding the treatment with a cleaning solution, it is known that a photoresist can be removed by using an alkaline cleaning solution. However, when the alkaline cleaning solution is brought into contact with a tungsten-containing material, it may be significantly damaged. Meanwhile, alkaline cleaning solutions capable of effectively removing a photoresist, wherein damage to a tungsten-containing material is reduced, have been proposed (Patent Documents 1, 4, 8 and 9), but these cannot suppress damage to a low-k film. Under such circumstances, it is desired to develop an alkaline cleaning solution capable of effectively removing a photoresist without damage to a tungsten-containing material and a low-k film.
Patent Document 1 proposes a wiring forming method using a cleaning solution containing potassium hydroxide, quaternary ammonium hydroxide, an organic solvent, pyrazole and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material while removing a photoresist, but damage to a low-k film cannot be suppressed. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Examples 6 and 7).
Patent Document 2 proposes a wiring forming method using a cleaning solution containing a fluorine compound, a metal corrosion inhibitor, a passivator and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material, but it is impossible to remove a photoresist and suppress damage to a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 8).
Patent Document 3 proposes a wiring forming method using a cleaning solution containing ammonium fluoride, gluconic acid and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material, but it is impossible to remove a photoresist and suppress damage to a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 9).
Patent Document 4 proposes a wiring forming method using a cleaning solution containing phosphoric acid, hydrochloric acid, amine, an alanine type surfactant and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material while removing a photoresist, but damage to a low-k film cannot be suppressed. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Examples 10 and 11).
Patent Document 5 proposes a wiring forming method using a cleaning solution containing hydrogen peroxide, a triazole and water. When using this cleaning solution, it is possible to suppress damage to a low-k film, but it is impossible to remove a photoresist and suppress damage to a tungsten-containing material. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 12).
Patent Document 6 proposes a wiring forming method using a cleaning solution containing hydrogen peroxide, quaternary ammonium hydroxide, quaternary ammonium salt and water. When using this cleaning solution, it is possible to suppress damage to a low-k film, but it is impossible to remove a photoresist and suppress damage to a tungsten-containing material. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 13).
Patent Document 7 proposes a wiring forming method using a cleaning solution containing amine, hydroxylamine salt, quaternary ammonium hydroxide, an organic acid, an organic solvent and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material, but it is impossible to remove a photoresist and suppress damage to a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 14).
Patent Document 8 proposes a wiring forming method using a cleaning solution containing N,N-diethylhydroxylamine, hydroxylamine, a water-soluble organic solvent, a metal anticorrosive and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material while removing a photoresist, but damage to a low-k film cannot be suppressed. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Examples 15 and 16).
Patent Document 9 proposes a wiring forming method using a cleaning solution containing an inorganic base, quaternary ammonium hydroxide, an organic solvent, azole and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material while removing a photoresist, but damage to a low-k film cannot be suppressed. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Examples 17 and 18).
Patent Document 10 proposes a wiring forming method using a cleaning solution containing hydrogen peroxide, hydrofluoric acid, an organic solvent, azole and water. However, when using this cleaning solution, it is impossible to remove a photoresist. Moreover, it is impossible to suppress damage to a tungsten-containing material and a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 19).
Patent Document 11 proposes a wiring forming method using a cleaning solution containing hydrofluoric acid, an organic solvent, azole and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material, but it is impossible to remove a photoresist and suppress damage to a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 20).
Patent Document 12 proposes a wiring forming method using a cleaning solution containing hydrofluoric acid, a silicon-containing compound, a surfactant, carboxylic acid, an anticorrosive and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material, but it is impossible to remove a photoresist and suppress damage to a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 21).
Patent Document 13 proposes a wiring forming method using a cleaning solution containing a sugar, a hydroxylamine, a quaternary ammonium compound, an organic acid and water. When using this cleaning solution, it is possible to suppress damage to a low-k film, but it is impossible to remove a photoresist and suppress damage to a tungsten-containing material. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 22).
Patent Documents 14 and 15 propose a wiring forming method using a cleaning solution containing an acid or salt thereof, a chelating agent containing nitrogen atoms, an organic solvent and water. When using this cleaning solution, it is possible to suppress damage to a tungsten-containing material, but it is impossible to remove a photoresist and suppress damage to a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 23).
Patent Document 16 proposes a wiring forming method using a cleaning solution containing an alkali and WzMXy (in the formula: M represents a metal selected from the group consisting of Si, Ge, Sn, Pt, P, B, Au, Ir, Os, Cr, Ti, Zr, Rh, Ru and Sb; X represents a halide selected from the group consisting of F, Cl, Br and I; W is selected from H, an alkali or alkaline earth metal, and a metal-ion-free hydroxide base moiety; y represents a number of from 4 to 6 depending on a metal halide; and z represents a number of 1, 2 or 3). However, when using this cleaning solution, it is impossible to remove a photoresist. Moreover, it is impossible to suppress damage to a tungsten-containing material and a low-k film. Therefore, this cleaning solution cannot be used for the above-described purpose (see Comparative Example 24). Further, a cleaning solution, in which WzMXy described in Patent Document 16 is blended in the cleaning solution of the present invention instead of the alkaline earth metal compound that is blended for the purpose of suppressing damage to the tungsten-containing material, cannot suppress damage to the tungsten-containing material and damages the low-k film (see Comparative Example 25).